Seekings, David
Crest publishing, 1999
Buku Referensi
Dunn, Frederick Sherwood
Johns Hopkins Press, 1929
Buku Teks
Wallwork, Adrian
Springer, 2010
Buku Teks SO
Cheong, Kwee Thiam
LexisNexis, 2016
Buku Teks
Branch, Alan E.
Chapman & Hall, 1979
Buku Teks